Can someone explain to me Black levels in a track

paul_w wrote on 3/3/2012, 10:00 AM
Hi all,
Its probably a simple matter of knowing what to do, but this has got me confused. I did not want to post this because i bet its super simple.. but here i am. Oh well.

So my usual workflow:
Edit footage on a track (or tracks), ok, thats fine..
To get correct 16-235 output from the render (to vimeo, youtube, DVD etc) apply Sony Levels Fx with "Computer RGB to Studio RGB conversion" to the main Video out buss.
Render it out...
Ok, so this works and my levels are good for vimeo etc..

But the problem:
If i use say the Legacy Text generator - or crop top and bottom of the track (making look a bit more like film aspect), the back areas are showing as computer (0) RGB EVEN with the levels fx (16-235) applied. Whats that about?
Or, just adjusting the track slider video level to 0 (black) also shows as 0 (not 16) in the waveform monitor.
My understanding was that once the fx was applied, ALL blacks then go to 16, and not 0? Also, if i use AAV colorLab, it does exactly that - but the Sony Levels does not.

Does that make sense?
How can i get all my blacks to show as 16.

thanks.
Paul.

Comments

john_dennis wrote on 3/3/2012, 10:42 AM
The Cliff's Notes version is:
If you put a 16,16,16 generated black on a track beneath your main tracks the effects won't go to 0,0,0 black.

The long answer is that it's more complicated. Check your scopes. There were discussions about the subject. Look at Laurence's contributions.
paul_w wrote on 3/3/2012, 10:54 AM
Thanks John, just reading posts now.

Does this mean we have to use 16,16,16 black media under every event with 0 black in it? Including any fade to blacks in the TL... hmm, this is not nice.

Will keep reading.

Paul.
Kimberly wrote on 3/3/2012, 10:58 AM
Hello Paul:

I'll take a stab at this even though the Gurus will likely have a better technical explanation.

Your problem may be solved by running a track of Legal Black (16) as the bottom most track in your project. When you add a Sony Solid Color of Black or White, note that the 16 and 235 limits, respectively, are obeyed. However when you add a Sony text media (Legacy or even the new ones) note the 16 limit for the background is not obeyed. That is because the background is not black, it is transparent. It looks black if there is nothing underneath it, but it is really the absence of color. So when there is absence of color, it cannot be limited by the Sony Levels FX.

Same thing when you crop. Around the edges you have the absence of color, not really black as it appears. Try running a solid color of say, red, under your Text Media and see what happens. Then change it to a legal black and see what happens.

I think this is what is going on.

Regards,

Kimberly
GlennChan wrote on 3/3/2012, 11:18 AM
What Kimberly said!

A single track on the bottom of black at 16 16 16 RGB will do... it will take 20 seconds or less to do.
paul_w wrote on 3/3/2012, 11:23 AM
Kimberly, thanks for that.

I half way understand it now:
"So when there is absence of color, it cannot be limited by the Sony Levels FX"..

Good point. I did know that the text generator blacks (transparent) and cropping frames would lead to 'no colour' in those areas so yes i see that.

But... and there's always a but!
I can use AAV colorLab instead of Sony levels and then my 0 blacks (and transparent areas) become 16, so its working with the blacks 'and' transparents. So it can be done without a 16 legal back track undernieth the TL using AAV. I find it odd that these two FX operate differently but i guess that may be simply the case.

Paul.
john_dennis wrote on 3/3/2012, 11:29 AM
If you have all computer RGB and you are applying the computer to studio levels filter, then you put a 0,0,0 black as the underlying track for your text and fades because you don't want the filter to convert 16,16,16 black to 32,32,32.

If you have legal blacks and you are not applying the computer to studio filter then use 16,16,16 underlying track.

If you have mixed legal and illegal media, it gets a little more complicated and you have to look at each event and overlap of the event individually.

Set up some test with the different scenarios, render and open the rendered files back in Vegas. Using the scopes on the rendered files will let you see the various results.
paul_w wrote on 3/3/2012, 11:39 AM
"If you have all computer RGB and you are applying the computer to studio levels filter, then you put a 0,0,0 black as the underlying track for your text and fades because you don't want the filter to convert 16,16,16 black to 32,32,32"..

Totally right, thanks for pointing that out. I do use the Levels filter, so the black media undernieth would be 0,0,0 (and later converted to 16,16,16 by the FX) I would have seen that problem imediately while viewing the waveform scope (which is always on display).

So my last question would be.. is this the norm for all NLE's ? or something specific to Vegas.. Do other NLE users also need this legal black track?..
open question to all.

Paul.
john_dennis wrote on 3/3/2012, 11:45 AM
Don't do other NLEs.
paul_w wrote on 3/3/2012, 11:48 AM
John, i do not understand that comment, dont do other NLEs ?

Paul.
john_dennis wrote on 3/3/2012, 12:01 PM
I don't do other NLEs.
paul_w wrote on 3/3/2012, 2:20 PM
Thanks everyone for your help. Going to try this later.

cheers
Paul.
farss wrote on 3/3/2012, 2:39 PM
Just so you don't get the wrong concept in yout head.
When or where there is nothing i.e. 100% transparency, as the result of Vegas's compositing, no FX will have any effect.

Bob..
paul_w wrote on 3/3/2012, 2:54 PM
..."no FX will have any effect"

but.. AAV ColorLab does.

but i see what you're saying, maybe its just something different about the way AAV works compaired to the other Vegas filters.

Paul.
NickHope wrote on 3/4/2012, 1:18 AM
I totally sympathise with your confusion Paul. I just tried a computer-RGB-to-studio-RGB FX on the master bus for the first time and was very surprised to see the scopes still showing black at zero. To my mind Vegas should have converted "nothing" to zero by the time the signal reaches the master bus.

If I were you, with your liking or detail and tinkering, I would give up on using computer-RGB-to-studio-RGB on the video bus and grade everything at event or track level.

Use a 16, 16, 16 underlay track, as others have advised, and set up presets for "Legal Black" and "Legal White" in both the solid media generator and the text generator.
WillemT wrote on 3/4/2012, 3:55 AM
Paul.

AAV does it wrong.

It changes the transparency if added to an event with transparency. You can check by placing any video event below a generated text event. Add a gray solid color below a generated text event. If you add AAV to the text event and select the "Convert to Studio RGB" preset, the the gray event below is also adjusted - the transparency is reduced to 16,16,16 - not the black. You definately do not want that - the event below should never be effected like that.

If there is no transparency in the event you apply AAV to, all is OK.

I agree when placing the Levels FX on the Master Video Bus, it should adjust the black, there is no compositing done on the Master Bus.

If you do not have another video event below the generated text you need to add a studio black event below. In fact it is good practice to always (assuming you need studio RGB output) place a studio black in the lowest track for the full length of the timeline. It caters for any fade to black etc. as well.

Willem.
paul_w wrote on 3/4/2012, 11:23 AM
Thanks both Nick and Willem,

The black track placed under the media tracks does indeed work, just testing it here and it does look fine on the scopes. So yes, we have a workable solution, thanks everyone for that.
AAV - with its fault (making transparent = black 0) does work also if placed in the video main bus. Yes, its a fault! but its actualy a nice fault to have in my case at least.
I agree, Vegas 'should' be converting transparent areas to 0 at the main bus for render out. There may be a reason why this has not been done in Vegas but i cant think what.
Out of interest, i tried a test with PP5. No problems at all, the output default is 16-235 no matter what you put on the timeline.. Thats nice and easy. Wish Vegas worked this way. Its actaully what i am aiming for using the Levels fx in the main bus, i have no need to render out to 0-255.

SCS, can we have 16-235 rendered files as default? (negating levels fx, black track etc)
and can transparent areas be converted to black 0 at render.

cheers.
Paul.
GlennChan wrote on 3/5/2012, 7:18 PM
So my last question would be.. is this the norm for all NLE's ?

Other NLEs handle all this levels stuff for you. (For the most part.) Even iMovie and Windows Movie Maker.

I really think that Vegas should do the same, but..... I guess most people don't request this feature and don't realize that they are doing things wrong. Please... make this feature request. The way Vegas handles levels is unintuitive and should be automated anyways.
johnmeyer wrote on 3/5/2012, 8:20 PM
I guess most people don't request this feature and don't realize that they are doing things wrong. Please... make this feature request. Good suggestion. I just dropped my request in the Sony Vegas "suggestion box."
Andy_L wrote on 3/5/2012, 8:59 PM
Can Sony possibly be unaware that this is a huge issue with Vegas? I always assumed there was some catastrophic reason (code, philosophy, legacy support ??) they couldn't change it. But the notion that it's never occurred to Sony to fix it doesn't seem likely to me...

On second thought, maybe the same people who built a preview window that shows incorrect levels think Vegas' levels handling is brilliant. :)
Haosen wrote on 3/6/2012, 3:07 AM
Normally, save the project files and quit the Vegas Pro, then re-start it.

Now you could see the video on the timeline.

Maybe there are some un-stable bugs on the RAM settings.

paul_w wrote on 3/6/2012, 7:17 AM
@johnmeyer, yep i also dropped this in the suggestion box. Would be nice to get Vegas in line with other NLEs. Its driving me nuts!

Paul.
Ros wrote on 3/6/2012, 7:26 AM
@johnmeyer, did it about 2 months ago and also added it to the Sony vegas survey few weeks ago.

Rob
farss wrote on 3/6/2012, 8:10 AM
All I can say is be careful you don't get what you wished for.

This is way more complex topic than many here seem to think.
Cameras today record video using a considerable array of values for black and white. We now have camera that use non linear gamma curves and have for a long time had 10bit video with all manner of compexity.

I agree, Vegas should handle all this correctly however it is not a trivial task.

Bob.
cbrillow wrote on 3/6/2012, 8:37 AM
I find the interplay between sRGB vs RGB/black levels/broadcast colors/video scopes to be exceptionally confusing. Can't tell you how many times I've changed my mind and re-rendered a file because I really don't know how to interpret what I'm seeing, and what is correct for subsequent display on a television set. (and it gets worse when factoring in CRT vs digital displays...)

I've read this thread, and I've read Glenn Chan's excellent treatises on the subject. At times, I think I understand what to do, and at others, I feel like a very old man who incapable of learning or understanding anything new.